Obstructive sleep apnea (OSA) is a serious disorder characterized by episodic obstruction of the pharyngeal airway accompanied by cessation or reduction in airflow. Untreated OSA has a negative impact 24 hours a day, disrupting nighttime sleep and causing excessive daytime sleepiness that interferes with functioning. Recent studies suggest that OSA and type 2 diabetes (T2DM) not only co-exist but that OSA may adversely affect glucose homeostasis. While physical activity is recognized as beneficial to persons with T2DM, OSA severity or daytime sleepiness may act to hinder persons with T2DM from participating in physical activity. The primary aim of this pilot/feasibility study is to obtain preliminary data to facilitate further hypothesis development and enhance the feasibility of conducting a double blind, randomized, placebo-controlled study to examine physical activity in subjects with T2DM and OSA who are treated with CPAP compared to subjects on sham-CPAP. The secondary aims are to explore: 1) the interrelationships of OSA severity, daytime sleepiness, and physical activity on glucose variability at baseline;2) average pre-post therapy changes in glucose variability in subjects treated with CPAP compared to subjects receiving sham-CPAP, and 3) pre to post therapy changes in weight, diet, residual sleepiness and mood in subjects treated with CPAP compared to subjects receiving sham-CPAP. The primary endpoint of the study, physical activity, will be measured by the Bodymedia SenseWear Pro Armband(R) to determine activity counts. The endpoint for glucose variability will be measured by the Medtronic Continuous Glucose Monitoring System (CGMS). Adherence to CPAP will be measured by a Smart Card(R) inserted in subjects'CPAP machines. We will limit the sample of subjects who are randomized to CPAP or sham-CPAP to persons with an adequate sleep duration pre-treatment (>6 hours), with moderate or severe OSA and with EDS to have a more homogenous, profoundly affected sample for this pilot study. The information that will result from the proposed study on of the effect of OSA and EDS on glucose variability has the potential to lead to the development of improved behavioral interventions in persons with diabetes. In addition, this study contains measures of diet and mood to begin to elucidate the possible effects of OSA and EDS on diabetes management. The study results from this R21 award will be used to inform the development and testing of a fully powered clinical trial that can test the efficacy of CPAP treatment on physical activity in persons with T2DM with the goal of improving diabetes outcomes. PUBLIC HEALTH RELEVANCE: Daily physical activity is important to achieve glucose control in persons with type 2 diabetes. The purpose of this study is to explore if obstructive sleep apnea and its daytime symptom, excessive sleepiness, act as barriers to physical activity. We will examine if treatment of obstructive sleep apnea with continuous positive airway pressure results in increased physical activity in persons with type 2 diabetes.